1. Field of the Invention
The present invention relates to an apparatus for aligning an optical waveguide and an optical fiber, and a method therefor, and more particularly, to an optical fiber passive alignment apparatus for passively aligning an optical fiber to be coupled with an input/output optical waveguide of an integrated optical device in which optical waveguide devices having various functions are integrated in a substrate, and a method thereof.
2. Description of the Related Art
In general, an optical fiber can be attached to an optical waveguide device by the following two methods. First, after waveguiding incident light into an optical fiber or device, the position of the optical fiber is precisely adjusted, and the optical power at the output port of the optical waveguide or optical filter is measured, to fix the optical fiber and optical waveguide in the maximum optical power state. This is called an active alignment method. On the other hand, without directing the light, the optical fiber and the optical waveguide are automatically aligned to be coupled with each other according to the shape or structure of those coupling portions, in what is called a passive alignment method.
The active alignment method has been common as a method of coupling the optical waveguide and optical fiber. The active alignment method requires a light source and a photodetector in order to align the optical fiber and optical waveguide. Also, the optical fiber and the optical waveguide may be precisely aligned with submicron accuracy with respect to an alignment axis having six degrees of freedom. Thus, the alignment is difficult and requires much time.
FIGS. 1A and 1B are a three-dimensional view and a side view illustrating a conventional passive alignment method. According to this method, a waveguide layer 101 is formed in a portion onto which an optical fiber is to be mounted of a planar substrate 100 such that a core center of the waveguide and a core center of the optical fiber match, thereby forming an optical fiber mounting portion 103 having a V-groove. Then, a groove is formed perpendicular to the optical fiber mounting portion 103 having the V-groove, such that the optical fiber 110 can be closely pushed against the optical fiber mounting portion 103 while being parallel with the optical waveguide. The cross-section of the optical fiber 110 is precisely ground, and the optical fiber 110 is mounted onto the optical fiber mounting portion 103 having the V-groove and pushed closely against the cross-section of the optical waveguide. Then, the optical fiber 110 and the optical waveguide are adhered to each other.
However, in the passive alignment method, because the diameters of the cores of the optical fiber and optical waveguide have dimensions within several a very precise shape and structure of the coupling portion, accurate positioning of the optical fiber end, and accurate cross-section grinding of the optical fiber end are necessary in order to reduce coupling loss. Thus, alignment is time-consuming and expensive.